Autodesk 00126-050008-1640A User Guide - Page 166

12 Tracing When tracing a raster line by picking, the program determines its type (line, arc or circle) and tries to trace the object to the greatest possible extent. The intersections of an entity with other objects are ignored, and the set of points representing the object is extended as long as the form of the raster object matches the recognized entity. Since real raster objects differ from ideal raster entities, the recognition algorithm uses the parameter Approximation Accuracy that sets the accepted level of deviation of the real raster object forms from the ideal ones. See the description of this parameter in section "Options tab", page 185. When tracing a raster entity, its intersections with crossing other objects are kept intact by the program. If the raster data selected during tracing is deleted, then the remaining raster objects are not broken. This allows you to replace raster objects with vectors without changing the form of other crossing raster objects, and also to allows you delete raster objects as if they were vector objects. For example, if a raster line intersecting a circle is deleted, the circle remains unbroken, the same as deleting a vector line lying over a vector circle. To trace an object with automatic type determination (Trace Auto) 1. Run tracing using one of the following methods: On the Raster to Vector toolbar click the Trace Auto button. -orFrom rConvert menu, choose a tracing mode, and then Auto. If some available raster images are inserted into the picture, then a selection dialog box appears. Select an image that you want to trace from this box. 2. You will see the following prompt in the command line: Pick point or [Line/Arc/Circle/Hatch/Symbol/Undo/Mode/Exit] : If you specify a raster object, then the automatic tracing will start. For the best results you should pick a point on the least distorted and on the longest segment of the raster object, far from its intersections with other objects. If the program recognizes a raster entity, then the object will be traced using the most appropriate object type. If the specified object is not a raster line arc or circle, then an approximating vector outline will be created. To distinguish raster lines from other objects WiseImage uses Max Width parameter (see page 183). If you select Enter, then the forced tracing by line model will start. By entering capitalized letters of the words listed in the prompt, you can modify the trace model, shift to another tracing mode, or cancel tracing during the operation. -or- You can choose a tracing model on the toolbar. It can be one of the following: Line/Arc/Circle/Hatch/Symbol. After recognition, the program shifts to the Trace Auto mode. 171